The New Rules of Fuel

Runner's World (UK) - - Front Page -

an in­ter­na­tional team of sports sci­en­tists led by Vin­cent Ony­w­era of Keny­atta Univer­sity, Kenya, spent a week mon­i­tor­ing ev­ery­thing a group of 10 top Kenyan male dis­tance run­ners ate and drank. To the sur­prise of no one, the re­searchers dis­cov­ered that the diet of these ath­letes was quite good over­all. They ate plenty of veg­eta­bles and healthy starches (mainly cab­bage, beans, corn­meal and pota­toes), a lim­ited amount of meat (mostly beef) and al­most noth­ing pro­cessed.

There was, how­ever, one no­table ex­cep­tion to the whole­some­ness of the reg­u­lar menu of these run­ners: a whop­ping 20 per cent of their calo­ries came from re­fined sugar. No, they weren’t snack­ing on sweets or swill­ing soft drinks all day. They just drank a lot of tea, which Kenyans like to take loaded with milk and ta­ble sugar. Still, 20 per cent is a lot – far more than the 12 per cent con­tri­bu­tion that re­fined sug­ars make to the diet of the av­er­age adult in the UK. This is, of course, con­sid­ered to be too high in sugar.

In the 13 years since this study was con­ducted, Kenya’s elite run­ners have con­tin­ued to fuel their bod­ies with su­per-sweet tea, some­thing I saw for my­self when I vis­ited the coun­try in 2015 to re­search my new book, Theen­durance Diet (Da Capo Life­long). These Kenyan elites, have, of course, con­tin­ued to per­form ex­cep­tion­ally well in com­pe­ti­tion. Mean­while, grow­ing num­bers of re­cre­ational run­ners in other parts of the world have striven to elim­i­nate sugar from their diet and even to avoid us­ing sugar-con­tain­ing prod­ucts dur­ing train­ing and com­pe­ti­tion. These ef­forts are based largely on a re­cent wave of neg­a­tive news re­port­ing on sugar, which has been la­belled a ‘drug’ a ‘toxin’ and ‘poi­son’ But if the best run­ners on earth are among the heav­i­est sugar con­sumers, can it re­ally be so bad?

Not ac­cord­ing to the ex­perts. ‘Sugar has be­come the scape­goat du jour in our pub­lic dis­course about nu­tri­tion,’ says Dr David Katz, Pres­i­dent of the Amer­i­can Col­lege of Life­style Medicine. ‘This is fine on one level, be­cause many of us eat too much of it and would ben­e­fit from eat­ing less. On an­other level, how­ever, this kind of ab­so­lutist, ei­ther/or think­ing about nu­tri­tion also car­ries neg­a­tive con­se­quences.’

For run­ners, the con­se­quences of an ex­ces­sive fear of sugar may in­clude fit­ness stag­na­tion re­sult­ing from in­ad­e­quate car­bo­hy­drate in­take (sugar is a carb) and also poor race per­for­mance re­sult­ing from fail­ure to take ad­van­tage of the per­for­manceen­hanc­ing ef­fects of sugar in­take dur­ing com­pe­ti­tion.

The truth about sugar is that it has pros and cons. On the plus side, it makes food taste good and it pro­vides quick en­ergy dur­ing in­tense ac­tiv­ity. On the mi­nus side, over­con­sump­tion of sugar has been proven to lead di­rectly or in­di­rectly to weight gain, in­sulin re­sis­tance and var­i­ous car­dio­vas­cu­lar dis­ease risk fac­tors. En­joy­ing the ben­e­fits of sugar while avoid­ing its neg­a­tives re­quires a bal­anced and smart ap­proach to sugar con­sump­tion. To find this bal­ance, fol­low these six sci­ence-based sugar rules.


There are two ba­sic cat­e­gories of sugar: nat­u­ral and re­fined. Nat­u­ral sug­ars are, as the name sug­gests, nat­u­rally present in foods. Ex­am­ples are lac­tose in milk and fruc­tose in fruit. Re­fined sug­ars are ex­tracted from nat­u­ral foods and then added to other foods and drinks to make them sweeter. Ex­am­ples are high-fruc­tose corn syrup, which is used in soft drinks, and su­crose (or ta­ble sugar), an in­gre­di­ent in many desserts.

Some nu­tri­tion ex­perts (and would-be ex­perts) cau­tion peo­ple to avoid nat­u­ral and re­fined sugar sources alike, on the grounds that ‘sugar is sugar’. Con­sider this quote from a pop­u­lar fit­ness web­site: ‘Some stud­ies sug­gest fruc­tose, the main type of sugar found in fruit, can even be more harm­ful than other sug­ars (namely, glu­cose). Fruc­tose has even been linked to in­creased belly fat, slowed me­tab­o­lism and over­all weight gain.’

It’s true that fruc­tose is the main type of sugar found in fruit. It’s also true that fruc­tose ap­pears to be more harm­ful than other types of sugar – but only when it’s not con­tained in fruit. Whole fruit it­self, how­ever, is one of the health­i­est things you can eat. A re­cent study at Har­vard Univer­sity, US, found that a high in­take of fruit was more ef­fec­tive than a high in­take of veg­eta­bles in pre­vent­ing weight gain.


Anti-sugar ac­tivists such as Gary Taubes, au­thor of The­casea­gainst Sugar (Por­to­bello Books), have pop­u­larised the idea that re­fined sugar, es­pe­cially fruc­tose, is uniquely po­tent as a con­trib­u­tor to weight gain and meta­bolic dis­eases. The bio­chem­istry un­der­ly­ing this ar­gu­ment is com­plex, but the ba­sic idea is that 100 calo­ries of sugar are more fat­ten­ing that 100 calo­ries of any­thing else you might eat.

The prob­lem with this idea is that most of the sci­en­tists ac­tu­ally do­ing the re­search it’s sup­pos­edly based on (Taubes is a sci­ence writer, not a sci­en­tist) don’t en­dorse it. ‘If you don’t overeat sugar, it doesn’t have any spe­cial ef­fect com­pared to any other form of car­bo­hy­drate,’ says Stephan Guyenet, a neu­ro­bi­ol­o­gist and au­thor of The­hun­gry­brain (Flat­iron Books).

Guyenet points to the work of John Sieven­piper, a nu­tri­tion sci­en­tist at the Univer­sity of Toronto and one of the world’s lead­ing ex­perts on the health ef­fects of sugar con­sump­tion. Sieven­piper’s re­search has yielded com­pelling ev­i­dence that re­fined

Many foods be­sides sweets also con­tain added sug­ars

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